Laminated pressed articles

ABSTRACT

A disk-shaped wafer is described which is based on an inorganic sorbent and a binder, with a thickness of less than 700 microns, which can be obtained by pressing a mixture of the inorganic sorbent, about 20 to 60% by weight of the binder and about 10 to 15% by weight water at a pressure of at least 70 MPa; and calcining the resulting green wafer at temperatures of at least about 500° C. until the water content is substantially removed.

RELATED ART

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 10/040,794, filed on Jan. 7, 2002, which claimspriority from Provisional Patent Application No. 60/260,282, filed onJan. 8, 2001.

FIELD OF INVENTION

The invention relates to disk-shaped wafers prepared from an inorganicsorbent and a binder, with a thickness of less than 700 microns, whichare characterized by high mechanical strength and low brittleness andwhich are able to effectively sorb inorganic and organic gases orvapors.

BACKGROUND OF INVENTION

The production of wafers, especially tablets, based on zeolites andbinders is already known. Thus, according to JP-A-61 15 5216, zeolitetablets are produced by mixing a zeolite, a binder and a lubricant andextruding the mixture. They are formed as tablets with the samedimensions in all directions.

JP-A-56063818 discloses production of zeolite tablets for use as gasadsorbents. Powdered zeolite dried at 105 to 110° C. are mixed with 8.1%by weight bentonite power and are kneaded with a 4% aqueous ureasolution. The mixture is tabletted, dried and calcined at 510° C. Theincrease in the compressive strength is dictated by the urea content.

JP-A-55 16 5144 discloses kneading zeolite powder for refrigerantaggregates in powder form with bentonite and water, extruding themixture and forming round particles with a diameter from 0.8 to 10 mm.

According to JP-A-55 10 4913, zeolite in the Na form is mixed with 25%by weight clay, kneaded with water, extruded, calcined at 650° C.,immersed in a calcium chloride solution, washed, dried at 110° C. andactivated at 400° C. The tablets are used as desiccants.

According to JP-A-603 2572, zeolite powder is mixed with kaolin and Na(or NH₄)-hydroxymethyl cellulose, shaped, dried and calcined at 650° C.,in order to increase the strength of the zeolite tablets.

According to JP-A-21 44 121, deodorants are prepared by extrudingzeolite powders or grains with calcium chloride or bentonite and water.The mixture is then tabletted and the tablets calcined.

According to JP-A-63 218 234, desiccants are produced by extruding amixture of microporous particles (for example, gypsum, cement, ceramicpowder) and an inorganic or organic filler, such as CaCl₂, LiCl,bentonite, zeolites, PVA or other water-soluble polymers. The mixture istabletted and then hardened.

According to JP-A-60 132 643, zeolite tablets are produced as desiccantsusing 20% sepiolite as the binder. The mixture is kneaded with water,tabletted, dried at 150° C. and calcined at 550° C. The tablets have animproved drying effect compared to bentonite tablets.

The tablets produced according to the prior art are unsuited for useunder spatially restricted conditions and under mechanical stress sincethey are too thick and too heavy and in terms of mass and surface, haveoverly low sorption capability for toxic gases and vapors. With theprocesses and mixtures according to the prior art, overly brittle wafersare obtained which crumble especially after calcining.

It is known that electroluminescent devices work properly over a longertime only when a desiccant is present. This can be attributed to thesensitivity of the electrodes, especially of the cathodes, for example,to moisture (the cathodes consist of Ca or Mg alloys). Therefore thesedevices are sealed as well as possible under a protective gas.

In EP 500 382 A2 the use of a moisture absorber in an electroluminescentdevice is described. The desiccant in the form of a powder or beads isapplied to a black silicone resin coating. According to the preferredembodiment the desiccant is placed in a gas-permeable bag.

U.S. Pat. No. 5,882,761 describes the use of a desiccant in anelectroluminescent device. BaO is used as the preferred desiccant. Seealso U.S. Pat. No. 5,591,379 which discloses a coating for use withmicroelectronic devices comprising a desiccant powder blended with abinder.

The sorbents known from the aforementioned publications have thedisadvantage that they can sorb only water vapor. An attack on thecathode can also be triggered by other gases which, in addition towater, form when the epoxy resin which is used for sealing sets(ammonia, volatile amines). In addition, the action of oxygen also canlead to failure of the luminescent components (oxidation of thecathode).

The object of this invention is to produce disk-shaped wafers based onan inorganic sorbent and an inorganic binder, with a very low thickness(less than 700 microns) which in spite of their low thickness have highstrength and thus can be installed, especially in electronic components,in which only limited space is available and which can be exposed tovibrations (for example, electronic display devices in motor vehiclesand mobile telephones).

This object is achieved by preparing a disk-shaped wafer based on atleast one inorganic sorbent and at least one binder, with a thickness ofless than 700 microns, which can be obtained by pressing a mixture of ora mixture containing an inorganic sorbent, about 20 to 60% by weight ofthe binder and about 10 to 15% by weight water (relative to the overallmixture) at a pressure of at least 70 MPa; and calcining the resultinggreen wafer at temperatures of at least about 500° C. until the watercontent is substantially removed.

The wafers as claimed in the invention have high strength, lowbrittleness, high sorption rate and high sorption capacity at low mass.They exhibit low thermal expansion, no wear and can be easily colored byadding pigments during manufacture.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of an electroluminescent product containing theplate shaped body of Example 10.

DETAILED DESCRIPTION

In order to obtain green wafers, as claimed in the invention, ofsufficient strength, the adherence to indicated limits for the mixingratio of the sorbent, binder, and water proportion and the compactionpressure is of extreme importance. In order to study the effect of themixing ratio of the sorbent and binders on the product properties, it isa good idea to use the weight ratio of the dry sorbent to the dry binderas a parameter to eliminate the different water contents of the varioussorbents and binders. Moreover, it is advantageous in the computation orestablishment of the water content to consider only the relativelyloosely bound proportion which can be determined by heating to 160° C.,since only the amount of this water influences the behavior of themixture in the pressing process and the quality of the final product,not the water which is structurally strongly bound by the sorbent orbinder.

To explain this concept the following examples are used. The sorbentzeolite 4A, as a commercially available powder, has a water content of20% by weight which water can only be completely removed above 500° C.In contrast, the binder bentonite, as a commercially available powderhas a water content of 12% by weight which can be completely removed at160° C. This is common knowledge to one skilled in the art.

If for example 70 parts zeolite 4A, 20 parts bentonite and 10 partswater are mixed, the weight ratio of dry sorbent to dry binder is(0.8*70)/(0.88*20)=3.2

The water content, as can be determined by drying the mixture at 160°C., is composed of the water which was added to the mixture (10 parts),and the water which is loosely bound to the bentonite:10+(0.12*20)=12.4

This mixture is accordingly determined to contain a weight ratio of thedry sorbent to the dry binder of 3.2 and a water content of 12.4% byweight.

If for example 25 parts zeolite 4A, 60 parts bentonite and 15 partswater are mixed, the weight ratio of dry sorbent to dry binder is(0.8*25)/(0.88*60)=0.4

The water content, as can be determined by drying the mixture at 160°C., is composed of the water which was added to the mixture (15 parts),and the water which is loosely bound to the bentonite:15+(0.12*60)=22.2

This mixture is accordingly determined to contain a weight ratio of thedry sorbent to the dry binder of 0.4 and a water content of 22.2% byweight.

When the wafers are calcined, besides the water which is loosely boundto the binder and the water which may be strongly bound by the sorbent,the water which is structurally bound to the binder can also bereleased. When using bentonite as the binder at the calcinationtemperature, the hydroxyl groups which are bound to the octahedrallycoordinated magnesium and aluminum ions are split off as water. Thetotal amount of water released during calcination thus depends on theratio of the sorbent to the binder, on the nature of the sorbent and thebinder, and the amount of water added. For example, in a mixture whichis formed from zeolite 4A as the sorbent and bentonite as the binder,the mixing ratio of the dry sorbent to the dry binder is 1.3 and thewater content is between 8 and 20% by weight. Between about 20 and 32%by weight is released as water during calcination.

Preferably the wafers are kept at the calcination temperature or anothersuitable elevated temperature until this amount of water has beenreleased and a constant weight has been achieved. Thus, according to onepreferred embodiment of the invention, drying or calcination takes placedown to a residual moisture content of <2% by weight (determined at thecalcination temperature).

According to one preferred embodiment of the invention it thus relatesto disk-shaped wafers containing at least one inorganic sorbent and atleast one binder, with a thickness of less than 700 microns, wherein inthe mixture the weight ratio of the dry sorbent to the dry binder isbetween 3.2 and 0.4. Preferably the water content of the mixture,determined at 160° C., is between about 8 and 22% by weight. The waferscan be obtained using a process in which the mixture containing theinorganic sorbent, binder, water and optionally pressing aids, ispressed at a pressure of at least 70 MPa and the resulting green wafersare calcined at temperatures of at least about 500° C. Preferablycalcination takes place up to a constant weight or up to a residualmoisture content of less than or equal to 2% by weight, determined atthe calcination temperature. The preferred mixing ratio of dry sorbentto dry binder is between about 2.1 and 0.7.

The wafers as claimed in the invention can be produced in automatedprocesses in large numbers per unit of time. They can be easily handledand can be removed from a storage container for example using aso-called “pick-and-place” machines and can be inserted into anelectronic device.

The wafers as claimed in the invention are able to sorb not only watervapor, but also other gases (ammonia, amines, oxygen). Since they have ahigh sorption capacity, the electronic device into which they areinserted need not be sealed completely airtight.

Preferably the inorganic sorbent constitutes a natural or artificialzeolite. Other sorbents can also be used, such as amorphous silicic acidor aluminum hydroxide and mixtures of inorganic sorbents.

In principle, any binder which seems suitable to one skilled in the artin this area can be used as the binder. Preferably a smectitic clay,especially bentonite, is used as the binder. Likewise the use of otherinorganic binders, for example aluminum oxide hydroxide(pseudoboehmite), is possible. Carbohydrate-based or protein-basedorganic binders can also be used, for example starch, cellulosederivatives (such as CMC or CEC), casein or also synthetic polymers suchas PVA, PVP or polyphenols or tannin-containing binders (quebracho).Mixtures of different binders can also be used.

Surprisingly, adding bentonite to the zeolite does not reduce thesorption capacity of the latter. In fact, a synergistic effect can beestablished, i.e. the absorption of water vapor by the mixture isreduced far less than could be expected purely according tocalculations.

The thickness of the wafer is preferably about 200 to 400 microns, itsbinder content is preferably about 40 to 50% by weight.

The subject matter of the invention is furthermore a process, especiallyfor producing the above defined wafers, which is characterized in that amixture containing the inorganic sorbent, about 20 to 60% by weight ofthe binder, about 10 to 15% by weight of water and 0 to 5% by weight ofone or more pressing aids is pressed at a pressure of at least 70 MPaand the resulting green wafer is calcined at temperatures of at leastabout 500° C. until the water is substantially removed. If the watercontent of the sorbent or binder used is already sufficient, it is notnecessary to add any additional water.

According to one preferred embodiment of the process, the ratio byweight of the dry sorbent and of the dry binder in the mixture isbetween about 3.2 and 0.4. The water content of the mixture, determinedat about 160° C., is preferably between about 8 and 22% by weight.

Preferred process measures are that the mixture is dried preferably to awater content of about 10 to 25% by weight, especially of about 12% byweight, whereupon the dried granulate is crushed, preferably to aparticle size of somewhat less than 250 microns.

It was found that when the mixture is pressed into a wafer the bestresults can be achieved when the mixture contains not more than 15% byweight, preferably not more than 8% by weight, especially 0% by weightof particles larger than 250 microns, preferably >200 microns andespecially preferably >150 microns. Moreover, the proportion ofparticles <45 microns should not be more than 50% by weight, preferablynot more than 30% by weight, and especially preferably not more than 20%by weight. The wafers produced in this way have especially advantageousphysical and chemical properties.

The preferably used A-zeolite is available in powder form and has amoisture content of about 10 to 22% by weight. The zeolite is mixed withbentonite powder with a moisture content of preferably about 10 to 20,especially about 12% by weight, and with water. This mixture is thengranulated.

The water content of the mixture depends on the properties of thebentonites. Enough water should be added to the bentonite/zeolitemixture so that the mixture can be granulated. Preferably ahigh-efficiency mixer is used for this purpose. The bentonite preferablyhas a montmorillonite content of >80% by weight.

Preferably a fatty-acid salt of a divalent or trivalent metal, such ascalcium or aluminum stearate, is used as the pressing aid.

The preferred pressing pressure is about 100 to 1300 MPa.

The wafers are calcined at about 500 to 900° C., preferably about 650°C., until a constant weight is reached.

The wafers can also be calcined under a vacuum, by which permanent gasessuch as oxygen are also sorbed.

Furthermore, the wafers can contain dyeing pigments, for example Fe₃O₄.

The subject matter of the invention is furthermore the use of the abovedefined wafers as inserts into electronic devices or components, such asdisplay devices, especially in electroluminescent components, such asorganic light-emitting diodes (LED). They can also be used inmoisture-sensitive liquid crystal displays (LCD).

These devices or components can also be damaged in their operation byexposure to inorganic or organic gases or vapors during production oruse, and as a result of their design have only very little spaceavailable for the sorbent.

These electronic devices or components (for example, display devices inmotor vehicles and mobile telephones) are often exposed to strongvibrations, for which reason it is important that the wafers do notbreak or crumble. Due to their strength it is not necessary to cover thewafers with a gas-permeable film, by which the production of electroniccomponents is simplified.

Compared to BaO, the volume and costs of the electronic component can besignificantly reduced. Thus, the wafers, relative to mass, have a highersorption capacity and sorption rate for water vapor in the requiredtemperature and moisture range within an electronic component. Moreover,when using BaO it must be considered that during the hydration reactionthe volume of the material increases by 100%. Therefore, within thecomponent, additional volume for the expansion of the desiccant shouldbe provided and between the BaO and the electroluminescent layer a film,which is permeable to water vapor and which prevents contact between theexpanding and possibly crumbling desiccant, and the layer should beplaced. Conversely, the wafers of the invention do not change volumewhen water vapor is absorbed and they remain mechanically stable, sothat the processes of making available an additional expansion volumewithin the component and attaching a protective film can be abandoned.

In addition, BaO has the disadvantage that it itself and its hydrationproducts react in a highly basic reaction. Moreover it heats up verydramatically on a local basis when moisture is absorbed and upon directcontact with organic compounds, it tends to self-ignite. This limits thechoice of polymers for the aforementioned protective film to veryexpensive ones, for example fluoropolymers, which thus raises the costof the component. Moreover, when using BaO, disposal problems arise,since as a chemical which is harmful to health, it makes disassembly,re-use and disposal of individual parts of the electronic component verydifficult.

The wafers as claimed in the invention can also be used for otherpurposes, for example as inserts in pharmaceutical packages, since inthis application only a limited volume is available for accommodating adesiccant.

The wafers can be present in any shape, for example, round, square,triangular or rectangular and can also contain holes and/or recesses.The wafers as claimed in the invention are free of dust and resistant towear. They can be produced in ordinary automatic pressing machines inlarge numbers per unit of time. Presses with multiple tools are used.

The invention is explained by the following examples.

EXAMPLE 1 Comparison

75.2 kg zeolite 4A (water content 20%), 23.6 kg bentonite (water content12%) and 1 kg calcium stearate are mixed in an high-efficiency mixer for2 minutes. Then water is added until the viscosity rises dramatically,and mixing continues for another 4 minutes. The mixture is dried at 110°C. to a water content of 12% and is then granulated (Stokes granulator)and screened (250 microns). 0.22 g of the material with a particle size<250 microns are pressed with a pressure of 69 MPa into a round wafer.The green wafers are calcined at 650° C. for three hours, cooled withthe exclusion of moisture, and packaged airtight. The thickness of thewafer decreases by about 15 to 25% during calcination.

Product Properties:

Thickness: 300 +/− 50 microns Moisture content <1% (after calcination):Scrap in production: >90% Drop test*: 100% fracture, wafer crumbles onthe edge *The so-called drop test is used as a measure for compressivestrength, 100 calcined wafers (round wafers with a diameter of 27 mm)being allowed to fall from a height of 1 m with the flat side down. Theprecentage of broken specimens is ascertained.

EXAMPLE 2 Comparison

57 kg zeolite 4A (water content 20%), 42 kg bentonite (water content12%) and 1 kg calcium stearate are mixed in an high-efficiency mixer for2 minutes. Then water is added until the viscosity rises dramatically,and mixing continues for another 4 minutes. The mixture is dried at 110°C. to a water content of 12% and is then granulated (Stokes granulator)and screened (250 microns). 0.22 g of the material with a particle size<250 microns are pressed with a pressure of 69 MPa into a wafer. Thegreen wafers are calcined at 650° C. for three hours, cooled with theexclusion of moisture, and packaged airtight.

Product Properties:

Thickness: 300 +/− 50 microns Moisture content <1% (after calcination):Scrap in production: 75% Drop test: 80% fracture

EXAMPLE 3

57 kg zeolite 4A (water content 20%), 42 kg bentonite (water content12%) and 1 kg calcium stearate are mixed in an high-efficiency mixer for2 minutes. Then water is added until the viscosity rises dramatically,and mixing continues for another 4 minutes. The mixture is dried at 110°C. to a water content of 12% and is then granulated (Stokes granulator)and screened on a 250 micron screen. 0.22 g of the material with aparticle size <250 microns are pressed with a pressure of 72 MPa into awafer. The green wafers are further treated as in Example 2.

Product Properties:

Thickness: 300 +/− 50 microns Moisture content <1% (after calcination):Scrap in production: <50% Drop test: 60% fracture

EXAMPLE 4

57 kg zeolite 4A (water content 20%), 42 kg bentonite (water content12%) and 1 kg calcium stearate are mixed in an high-efficiency mixer for2 minutes. Then water is added until the viscosity rises dramatically,and mixing continues for another 4 minutes. The mixture is dried at 110°C. to a water content of 12%, is then granulated (Stokes granulator) andscreened on a 250 micron screen. 0.22 g of the material with a particlesize <250 microns are pressed with a pressure of 350 MPa into a wafer.The green wafers are calcined at 650° C. for three hours, cooled withthe exclusion of moisture, and packaged airtight.

Product Properties:

Thickness: 300 +/− 50 microns Moisture content <1% (after calcination):Scrap in production: <25% Drop test: 15% fracture Sorption capacity*after one hour: 5.4% by weight after 5 hours: 7.2% by weight after 24hours: 13.0% by weight *The sorption capacity for water vapor isdetermined at 25° C. in an atmosphere with 10% humidity.

EXAMPLE 5

The procedure from Example 4 was repeated with the difference thatcalcination of the green wafers took place in a vacuum. The calcinedwafers had essentially the same product properties as the wafers fromExample 4, but in addition exhibited an absorption capacity for oxygenof about 5 ml/g (determined in a dry oxygen atmosphere).

EXAMPLE 6

56.9 kg zeolite 4A (water content 20%), 41.5 kg bentonite (water content12%), 1 kg calcium stearate and 1 kg quebracho are mixed in anhigh-efficiency mixer for 2 minutes. Then water is added until theviscosity rises dramatically, and mixing continues for another 4minutes. The mixture is dried at 110° C. to a water content of 12% andis then granulated (Stokes granulator) and screened (250 microns). 0.22g of the material with a particle size <250 microns are pressed with apressure of 200 MPa into a wafer. The green wafers are calcined at 650°C. for three hours, cooled with the exclusion of moisture, and packagedairtight.

Product Properties:

Thickness: 300 +/− 50 microns Moisture content <1% (after calcination):Scrap in production: <35% Drop test: 10% fracture

EXAMPLE 7

The procedure from Example 4 was repeated with the difference that thepressure used in pressing was 1200 MPa. The drop test yielded 10%fracture. Scrap was <10%.

EXAMPLE 8

The procedure from Example 4 was repeated with the difference that 64 kgzeolite 4A, 40 kg bentonite, 5 kg Fe₃O₄ and 1 kg calcium stearate wereused. The resulting wafers were dark colored and could be used in a LEDdisplay as a contrast surface.

EXAMPLE 9

57 kg zeolite 4A (water content 20%), 42 kg of a 50/50 mixture ofattapulgite and kaolin (water content 12%) and 1 kg calcium stearate aremixed in an high-efficiency mixer for 2 minutes. Then water is addeduntil the viscosity rises dramatically, and mixing continues for another4 minutes. The mixture is dried to a water content of 12%, is thengranulated and screened on a 150 micron screen. 0.17 g of the materialwith a particle size <150 microns are pressed with a pressure of 200 MPainto a wafer. The green wafers are calcined at 650° C. for three hours,cooled with the exclusion of moisture, and packaged airtight.

Product Properties:

Thickness: 300 +/− 50 microns Moisture content <1% (after calcination):Scrap in production: 25% Drop test: 70% fracture

EXAMPLE 10

An organic electroluminescent component 1 (square, surface 12.9 cm²), asshown in FIG. 1, is produced using a wafer (round, diameter 27 mm) fromExample 4. After the wafer 2 is mounted on the back wall 3 of thecomponent, it is attached using an adhesive 4 to the glass substrate 5of the component and sealed as much as possible using the adhesive. Thena microscopic photograph (magnification 50×) of the light emitting part6 (consisting of the anode 7, the light emitting layer 8 and the cathode9) of the component is taken. This photograph [not included] does notshow any dark (non-luminous) specks which would indicate an attack onthe cathode 9.

The component is exposed to a temperature of 85° C. and a relativehumidity of 85% for 500 h. Then a microscopic photograph of the lightemitting part 6 of the component 1 is taken again. Comparison of the twophotographs [not included] shows that no dark specks formed which wouldindicate an attack on the cathode 9.

EXAMPLE 11 Comparison

An organic electroluminescent component 1 as in Example 9 as shown inFIG. 1 is produced using BaO. The covering for the BaO is awater-permeable teflon film which is attached to the rear wall 3 of thecomponent using thin, two-sided adhesive tape. The amount of BaO is setsuch that the total mass of the BaO, the teflon film and thedouble-sided adhesive tape corresponds exactly to that of the wafer usedin Example 9. Then, as described in Example 9, magnified photographs ofthe light emitting part before and after storage for 500 h at 85° C. and85% humidity are taken [not included]. Comparison of the two photographsshows the distinctly recognizable growth of dark points which indicatean attack on the cathode 9.

1. A disk-shaped wafer which is obtained by a process comprising the steps of compressing a mixture, comprised of an inorganic sorbent, about 20 to about 60 percent on a dry weight basis of a binder and about 10 to about 15 percent by weight water, wherein the quantity of the water is based on its overall content in the mixture at a pressure of at least 70 MPa to form a green wafer, and calcining the resulting green wafer at a temperature of at least about 500° C. until the water present in the calcined wafer comprises less than about 2 percent of the calcined wafer, by weight, wherein the thickness of the calcined wafer is less than about 700 microns.
 2. The disk-shaped wafer of claim 1 wherein the weight ratio of the sorbent to the binder on a dry weight basis in the mixture is from about 3.2:1 to about 0.4:1.
 3. The disk-shaped wafer of claim 1 wherein the green wafer is calcined until the wafer has a substantially constant weight.
 4. The disk-shaped wafer of claim 1 wherein the inorganic sorbent comprises a natural or synthetic zeolite or mixtures thereof.
 5. The disk-shaped wafer of claim 1 wherein the binder comprises a smectite clay.
 6. The disk-shaped wafer of claim 1 wherein the binder comprises bentonite.
 7. The disk-shaped wafer of claim 1 wherein the thickness of the calcined wafer is from about 200 to about 400 microns.
 8. The disk-shaped wafer of claim 1 wherein the binder comprises from about 40 to about 50 percent by weight of the mixture prior to compressing.
 9. The disk-shaped wafer of claim 1 wherein the pressure placed on the mixture is from about 100 to about 1300 MPa.
 10. The disk-shaped wafer of claim 1 wherein the mixture further comprises a pressing aid.
 11. The disk-shaped wafer of claim 10 wherein the pressing aid comprises a fatty acid salt of a divalent or trivalent metal.
 12. The disk-shaped wafer of claim 1 wherein the binder comprises a tannin-containing binder.
 13. The disk-shaped wafer of claim 1 wherein the binder comprises quebracho.
 14. The disk-shaped wafer of claim 1 wherein the green wafer is calcined substantially under a vacuum.
 15. The disk-shaped wafer of claim 1 wherein the mixture further comprises a dyeing pigment.
 16. The disk-shaped wafer of claim 1 wherein the water content of the mixture determined at a 160° C. prior to compressing is from about 12 to about 22 percent by weight.
 17. The disk-shaped wafer of claim 1 wherein the water content of the mixture determined at a 160° C. prior to compressing is from about 8 to about 22 percent by weight.
 18. A process for producing a disk-shaped wafer comprising preparing a mixture containing at least one inorganic sorbent, about 20 to 60 percent by weight of at least one binder and about 10 to about 15 percent by weight water, compressing the mixture at a pressure at least 70 MPa to produce a green wafer, and calcining the green wafer at a temperature of at least about 500° C. until the water content of the resulting disk-shaped wafer is less than about 2 percent by weight and its thickness is less than 700 microns.
 19. The process of claim 18 wherein the weight ratio of the sorbent to the binder in the mixture on a dry weight basis is from about 3.2:1 to about 0.4:1.
 20. The process of claim 18 wherein the calcination step is continued until the green wafer has a substantially constant weight.
 21. The process of claim 18 wherein the water content of the mixture determined at 160° C. prior to compressing is from about 12 to about 22 percent by weight.
 22. The process of claim 18 wherein the water content of the mixture determined at 160° C. prior to compressing is from about 8 to about 22 percent by weight.
 23. A process for sorbing inorganic and organic gases or vapors from an electroluminescent device comprising placing the calcined, disk-shaped wafer of claim 1 within the electroluminescent device and closing the electroluminescent device. 